Engine Core Theory

[Jeep Driver]

Jeep 2.5L Engine (91-96) - $450 (Sadieville, ky)

 

I have a Jeep 2.5L block, crank and head. All three have been cleaned and machined. The block has been bored, the crank turned down, and the head milled and a valve job. You can buy it complete or by part:

Block - $250

Crank - $100

Head - $100

All - $ 450 cash

 

 

 

Above is an example of several possibilities or offerings.

 

I'm considering a '97 2.5 complete non-running engine that is about 2 hours away for $180. If it's not sold by Fri I'll pick it up over the weekend.

 

My theory is this-

I want to rebuild a core that is complete as a factory engine, keeping the crank and rods and head together. Theory being that if a rotating assembly that has been mated for 10 years and 100K miles.....it is a proven assembly.

 

VS.

 

Acquiring an assortment of parts from assorted engines........ie......crank kit.....etc.....

 

 

I'm also concerned about buying parts that have been machined by unknown machine shops.

 

 

 

 

If it were you......?

 

Thanks

[88ComancheMitch]

I can agree with your theory. But if you're going to have the block and head checked out by a machine shop, it shouldn't matter. I'm guessing you're not wanting to go to the machine shop though.

 

 

I'd say unless you cab hear it run anything is just add likely as the next.

[Strokermjcomanche]

I'd just get a low mileage complete engine . Theyre out there just be patient . Unless you plan on building the engine for performance/ racing . The low mileage engine should be less money in the long run .

 

Just checked my local jeep jy and they have a 2.5 out of a 99 tj with 90 k for$ 750

[Jeep Driver]

I can agree with your theory. But if you're going to have the block and head checked out by a machine shop, it shouldn't matter. I'm guessing you're not wanting to go to the machine shop though.

 

 

I'd say unless you cab hear it run anything is just add likely as the next.

Yes, it is going to the machine shop but I want to be the one that chooses the shop and decides what work is done to it.

[Jeep Driver]

I'd just get a low mileage complete engine . Theyre out there just be patient . Unless you plan on building the engine for performance/ racing . The low mileage engine should be less money in the long run .

 

Just checked my local jeep jy and they have a 2.5 out of a 99 tj with 90 k for$ 750

Double roller timing set and cam is on the order list.

And I want to discuss with the machinist what head work is to be done.

[Jeep Driver]

http://www.jegs.com/i/Mopar+Performance/312/P5249519/10002/-1?CAWELAID=1710533392&CAGPSPN=pla&gclid=Cj0KEQjw6pGfBRD09M-TmYTBzqIBEiQAcRzH50RE83a3Ciw_FiC68iApOM0E9vNufgUUp3ELqkNRLc4aArcw8P8HAQ

 

http://www.hesco.us/products/7724/new-products/167924/rvob4-25l-camshaft#.U-G9bP6lW78

 

http://www.quadratec.com/products/17601_502_07.htm

[Jeep Driver]

What pistons are you 4.0 guys using?

[Eagle]

 

Jeep 2.5L Engine (91-96) - $450 (Sadieville, ky)

 

I have a Jeep 2.5L block, crank and head. All three have been cleaned and machined. The block has been bored, the crank turned down, and the head milled and a valve job. You can buy it complete or by part:

Block - $250

Crank - $100

Head - $100

All - $ 450 cash

 

 

Above is an example of several possibilities or offerings.

 

I'm considering a '97 2.5 complete non-running engine that is about 2 hours away for $180. If it's not sold by Fri I'll pick it up over the weekend.

 

My theory is this-

I want to rebuild a core that is complete as a factory engine, keeping the crank and rods and head together. Theory being that if a rotating assembly that has been mated for 10 years and 100K miles.....it is a proven assembly.

 

VS.

 

Acquiring an assortment of parts from assorted engines........ie......crank kit.....etc.....

 

 

I'm also concerned about buying parts that have been machined by unknown machine shops.

 

 

 

 

If it were you......?

 

Thanks

 

Whatever makes you feel happy. But consider what is actually "mated" in an internal combustion engine. The rods and pistons basically don't contact the block, the "mated" parts are the rod bearings and piston rings. The crank doesn't mate directly to the block, it only "matesd" to the crank bearings. If you're doing a rebuild, you'll be replacing the rod and main bearings and piston rings anayway, so any previous mating will be gone, and you start from ground zero.

 

Hopefully the pistons never touch the head, and in a rebuild you check the head for flatness and have it trued if it's not flat, so mating the head to the block isn't a requirement. And the head and block don't actually "mate" anyway -- there's a gasket separating them.

[johnj92131]

I am doing much the same thing to build a stroker.  But I am buying parts to be machined back into factory specs.  I got a 98 short block for $200 just for the rods and the block.  This weekend I am going 150 miles away to buy a 258 long block just for the crank and the con rods.  The crank may or may not be salvagable.  But for $75 it is worth a shot. $95 more to grind the crank, $11 to rebuild each con rod.  Piston? Still looking, may go cast for under $200  or up to $500 for forged pistons.  New stock 97 cam and timing chain, gasket kit.   The cylinder head will be a bit of a challenge. Buying a used late cylinder head could mean buying a cracked cylinder head.  But the late small exhaust port may be the best head for low end torque.  $50 will get me a used H.O. head and for a couple of hundred the machine shop will make it good as new.

 

Why am I doing this?  Because I purchased a "good running" engine that turned out to have a badly scored main bearing.  To me that is the problem with a used engine.  You don't really know what you are buying.  Sometimes it works out OK, sometimes not quite as OK as you want.  But it is a used engine, right.

 

For about $2K, I expect to have a new factory specification engine ready to go for at least 200K miles. And it will put out 15-20% more low end torque than the stock engine.  Only thing I could do better would be to supercharge the engine.

[sloride]

Get an old complete engine on the cheap cheap and rebuild using a trusted machine shop.  OR get the parts and assemble your own engine using a trusted machine shop.  Its probably going to be a crap shoot either way.  Experience has taught me just because an engine has been mated together for life, doesn't necessarily make it a good thing...........  In the end it all comes down to knowing the parts you have and going over them with a fine tooth comb, that and of course having a good reliable machine shop.

[outlaw star]

What pistons are you 4.0 guys using?

I was using Weisco ones.

[outlaw star]

With any used engine, I always tear it down to inspect everything.

[Jeep Driver]

 

 

Jeep 2.5L Engine (91-96) - $450 (Sadieville, ky)

 

I have a Jeep 2.5L block, crank and head. All three have been cleaned and machined. The block has been bored, the crank turned down, and the head milled and a valve job. You can buy it complete or by part:

Block - $250

Crank - $100

Head - $100

All - $ 450 cash

 

 

Above is an example of several possibilities or offerings.

 

I'm considering a '97 2.5 complete non-running engine that is about 2 hours away for $180. If it's not sold by Fri I'll pick it up over the weekend.

 

My theory is this-

I want to rebuild a core that is complete as a factory engine, keeping the crank and rods and head together. Theory being that if a rotating assembly that has been mated for 10 years and 100K miles.....it is a proven assembly.

 

VS.

 

Acquiring an assortment of parts from assorted engines........ie......crank kit.....etc.....

 

 

I'm also concerned about buying parts that have been machined by unknown machine shops.

 

 

 

 

If it were you......?

 

Thanks

 

Whatever makes you feel happy. But consider what is actually "mated" in an internal combustion engine. The rods and pistons basically don't contact the block, the "mated" parts are the rod bearings and piston rings. The crank doesn't mate directly to the block, it only "matesd" to the crank bearings. If you're doing a rebuild, you'll be replacing the rod and main bearings and piston rings anayway, so any previous mating will be gone, and you start from ground zero.

 

Hopefully the pistons never touch the head, and in a rebuild you check the head for flatness and have it trued if it's not flat, so mating the head to the block isn't a requirement. And the head and block don't actually "mate" anyway -- there's a gasket separating them.

 

 

 

Yeah.......I guess........

 

When I posted this- I had just got off the phone with a guy who had a pan that I will need, he also stated that he has a 'new' head that I can pick up...make offer he says.

The head he bought for a rebuild that never happened and he "just wants it out of the way".

I figure I can pick up for $100.

 

I spend $100 today to save $100 tomorrow that costs me $400 a month from now.......that is my concern.

 

I can only spend my money once.

 

 

I have only rebuilt two other engines, both were complete.

 

When I dropped the pan on mine the rods were clearly marked by number and direction, the engine had been rebuilt and at least the builder had the sense to return the rods to their original location as I had done the same in the past.

That was what was in the back of my mind when I asked about assemblies.